In existing reinforced concrete elements such as concrete slabs, beams, columns and walls, it is sometimes desirable to strengthen the element for one or more reasons. For example, the applied loading requirements may exceed the original design values for the element, or the load carrying capacity of the element may have been reduced due to deterioration, or the element may require increased stiffness for less deflection. The element may also require lower working stresses to reduce fatigue, or may require upgrading to withstand higher seismic and/or blast loading.
One form of strengthening existing reinforced concrete elements is by laminating or bonding a mat or strip of composite material with carbon or glass fibers to the surface of the concrete element where bending occurs. However, it is undesirable for the composite mat or strip to be exposed to the weather and/or to traffic such as on the top surface of a concrete bridge slab. For example, if water seeps between the composite mat or strip and the concrete surface, it is possible for the mat or strip to delaminate from the concrete surface if the water freezes. It is also necessary to prepare the concrete surface in order to obtain a good bond of the reinforcing mat or strip to the concrete surface.